1. Field of the Invention
The present invention relates to a flexible display device, and more particularly, to a flexible display substrate used in a flexible display device capable of relieving stress concentrating on a wire upon bending a substrate.
2. Discussion of Related Art
Display devices used in monitors of computers, televisions (TVs), and cell phones include organic light emitting display devices (OLEDs) and plasma display panels (PDPs), both of which autonomously emit light, and liquid crystal display devices (LCDs) requiring a separate light source, etc.
Recently, flexible display devices capable of being bent or curved have gained much attention as the next-generation display device. Flexible display devices offer unique features that conventional rigid display devices do not have. Even with limited flexibility, these devices provide a slimmer form factor, lighter weight, higher durability, and most of all, the freedom of design for portable electronic devices such as cell phones and multimedia players. With enhanced flexibility, a range of revolutionary display and lighting opportunities can be created. These opportunities include new electronics products such as TVs with curvature adjustable screen as well as portable electronics with a rollable display screen.
However, many factors need to be considered for the development of next-generation flexible-display technology. In a sense, flexibility means ability to withstand strain from being bent, but many parts of the flexible display devices still face the stability issues. For example, electrodes and wires in the flexible devices are often formed with indium tin oxide (ITO). ITO, however, is brittle and therefore prone to cracking when deformed, whereas the underlying substrate is ductile and flexible. Cracking of the electrodes and wires causes spots of poor or no contact and eventual loss of functionality over large areas of the display devices, and thus is one of the major concerns in flexible display devices. Even when conductive polymers or carbon based coatings are used to form the electrodes/wires, mechanical stress (i.e., tensile/compression stresses) remains.